ON THE CAE GWYN CAVE. 129 



even during the recent excavations. Under these circumstances there 

 was no wonder that the cave-deposits so nearly resembled the drift as 

 to be considered by some a continuation of the marine beds. 



There was no difficulty in accountinj^ for the character of the 

 contents oi the cave on the hypothesis that the drift already covered 

 a great part of the surface of the rock while the cave was being 

 filled. But on the supposition that the drift sealed the mouth of a 

 filled-up cave, how can we explain the occurrence in the cave of 

 material which must have been derived from that drift, such as the 

 flints which occurred in the lowest bone-earth ? 



Some account for this by supposing that the sea broke up stalag- 

 mitic floors and mixed up preexisting cave-deposits with drifted sand 

 and Bonlder-clay ; but there was no trace of such action in the cave. 

 The principal masses of travertine were in the line of the most 

 recent drainage to the north, where the water disappears now. 

 This continuation of the cave is indicated by the dark shades in the 

 lower right hand of fig. 4, and the lower left hand of figs. 2 and 3. 



There were no sea-shells in the cave. Curiously, we did not 

 happen to find even one carried in through the swallow-holes. 

 It may be that all the shells perished in that process. But 

 had they been deposited fresh by the sea in the bone-earth, they 

 would have been preserved. The material was not arranged as it 

 usually is in sea-caves, tossed up into sloping banks of shingle ; it 

 was an ordinary cave-deposit, and all the phenomena could be simply 

 explained by reference to what are known to be the common pro- 

 cesses of subterranean denudation. 



It has been frequently stated that the sands of the drift outside 

 the cave passed uninterruptedly into the cave. I saw the material 

 that closed the opening before anything was known as to the nature 

 of the drift immediately beyond. I saw in it no such sand, except 

 the recently scraped sand on the very top of the cave-deposits along 

 the rabbit-burrows. I prodded vertically upwards into clay, oppo- 

 site to where sand occurred in the section outside. It is quite clear 

 that sand would not have stood in such a position. The next thing 

 that happened was that a plug of clayey sludge descended into the 

 cave and cut off all further observations for some time. Yet, on the 

 occasion of my last visit to the cave, the continuity of the sand with 

 the upper beds in the cave was again asserted. I asked how that 

 opinion could be reconciled with the admitted fact of the settlement 

 of the plug of clay before we had got through the cave into the 

 drift outside, but could get no satisfactory answer. The fact is that 

 the material inside the cave did much resemble the drift outside, 

 but that was simply because it was derived from it by swallow-hole 

 action, and is an argument in favour of the view that the drift must 

 have been outside during the whole of the time of the accumulation 

 of the deposits in the caves, and not that the marine- drift sealed up 

 the mouth of a previously filled cave. 



The section in the Brit. Assoc. Hep. 1886, p. 219, is not a section 

 seen at the opening of the cave, but of what was seen after the 

 actual mouth had been cleared. It is a section of the drift which 



Q.J.G. S. Ko. 173. K 



